How do you get Surfcam to handle STL files? When we ask them about it they
can't do it.

Some cad packages are better at editing imported data than others. Catia,
Imageware and The new version of Pro/e (with some options) can all make non
parametric changes to IGES data. You can modify surfaces ect.

That is a good question. As you said, since scanned data is transferred
to a CAD system as a generic surface model, it will not be a model that
is native to that CAD package and therefore not easily editable.
Although you cannot make parametric changes such as modifying dimensions
and features, you can do some editing such as cutting holes in the
surface, and adding geometry. Typically, if the goal is to create a
complete parametric model in your CAD system, the imported data is used
as a template upon which the native geometry is created. There are,
however, some tools that can make this easier. For example, there is an
add-on for SolidWorks called FeatureWorks that does a good job of
automatically recognizing geometric features in the generic model and
creating the native features (holes, fillets, extrusions, etc.).
http://www.solidworks.com/html/Products/featureworks.cfm

That being said, it is not always necessary to create a completely
native, parametric CAD model from the scanned data, depending on your
use for the data. If it is going to be used to program a CNC machine to
create the part, a generic surface model in IGS format is typically
sufficient for most CAM software that toolmakers use (assuming the
surface model represents what you want to be built, and doesn't need
modification). Additionally, some toolmakers are now simply using an
STL file (polygon mesh) to create a program (using a CAM software such
as SurfCAM), which is much simpler to create from scan data and
eliminates the need to create a NURBS surface.

On a related note, you can use a manual touch probe digitizer (FaroArm,
Microscribe) to reverse engineer a part DIRECTLY into many CAD packages
including SolidWorks, thereby giving you a completely editable model.
However, there are some tradeoffs between this process and other types
of scanning, depending on the nature of parts you are reverse
engineering.

I hope this is helpful. I'm sure there is more information on this
topic that others can provide - I look forward to hearing other input.

We have recently had a part scanned, tweaked, and provided back to us as
a SolidWorks file. The geometry is perfect but it's a dumb solid. Our
customer is trying to modify the part (i.e.. add bosses, thicken
sections, make a few cuts, etc. ) but is not having any luck.

My question is directed at those who do this type of work on a regular
bases. How do you go about working with the "dumb solid" in-lieu of a
fully parametric solid? Are there tricks to working with the "dumb
solid" that has been imported back into the CAD package that allow for
meaningful data to be sent to tool makers?